1. Field of the Invention
The present invention relates to machine control and, more specifically, to a system and method for high speed control and rejection of out-of-specification products during a manufacturing process.
2. Description of the Related Art
In all phases of manufacturing, quality control has become an issue of increasing importance for many reasons, including, of course, a desire to produce a quality product which will satisfy consumer demand and for which consumers will be willing to pay a reasonable price. However, quality control in the manufacturing process can also help manage production costs, can speed the manufacturing process, and can avoid problematic issues with the finished product following the manufacturing process.
While much of the following discussion is directed to the details of implementing the present control and rejection system within cigarette manufacturing and packaging processes, the preferred features of exemplary embodiments of the invention are applicable to many types of processing and production environments where quality control and high speed management of the production and/or manufacturing process is important.
Contemporary cigarette manufacturing, or making, is a high speed process wherein literally thousands of individual cigarettes can be made from shredded tobacco, rolls of cigarette paper, and, optionally, filters, each minute on individual cigarette making machines. Hauni and Molins are just two of the suppliers of cigarette making equipment to the cigarette manufacturers throughout the world. FIG. 1 shows an example of a cigarette making machine 100, wherein tobacco enters the machine at 102, is wrapped with cigarette paper at 106 forming a continuous rod, cut into single or double-length cigarettes at 108, appended with filters from hopper 120, and ultimately output at 110 to be packaged into packs and cartons of cigarettes. At various points along the continuous production line represented by stations 102–110, sensors detect various conditions related to the quality and make-up of the cigarette. For example, 112 represents a sensor location that determines the density of the tobacco rod forming a particular cigarette. If the rod is determined to be too heavy, for example, then too much tobacco is being used, which can be wasteful and, accordingly, expensive to the manufacturer. In response to the determination that the rod is too dense or too heavy, a control signal can be sent to a trimmer at location 114 to adjust the amount of tobacco being shaved from the tobacco flow, thereby thinning the flow to acceptable specifications. Similarly, at 116 a sensor can detect the dilution value for individual cigarettes by sensing the amount of resistance necessary to draw a flow of air through the finished cigarette. If the resistance is outside the specification range as being too high or too low, that particular cigarette is flagged for ultimate ejection at a rejection station 118. Further sensors can detect, for example, whether any metal is present in the tobacco, whether there is a splice in the cigarette wrapping paper, whether an end of a cigarette rod has loose tobacco, or whether the filter is properly attached or is missing.
Therefore, during the high speed manufacture of cigarettes and like products, quality control parameters can be sensed and reactive measures can be taken to modify the production process or reject the out-of-specification products, all without shutting down the production line. To accomplish this control and rejection process in present day cigarette making machines, special purpose controllers (hereinafter “SPC's”) are utilized to interpret the signals from the various sensors, such as sensors 112 and 116, and determine, through processor(s) within the SPC's, appropriate action to take. While not expressly shown in FIG. 1, each SPC is typically located within the manufacturing device relatively close to the sensor providing input to the SPC. One problem with this technique is that the SPC's are typically designed to control and./or measure only one parameter in the manufacturing process. If more than one parameter needs to be measured or controlled, separate SPC's must be utilized for each parameter. Furthermore, SPC's have limited memory, which acts to compromise both the functionality of the SPC and the retention of sensory and processing data. Additionally, SPC's are relatively expensive, in that a typical SPC for a single function can cost over $10,000. More importantly, however, SPC's are limiting in that a single SPC assembly, including a processor, memory, and input/output (hereinafter “I/O”) circuitry, is typically dedicated to a single function, such as sensing the weight or density of the tobacco rod at 112. The components comprising the SPC assembly are often specifically selected for the particular sensing and control function, with specific circuit boards, wiring, components, and switch settings being selected based on the intended function of that SPC. Modification, adjustment, and repair of the SPC's is therefore difficult, time-consuming, and expensive, often requiring physical intervention at the SPC itself, which in turn often requires shut-down of the production line.